Generally, by organizing a plurality of disks into a disk array according to a certain form and scheme, it may be possible to obtain a higher speed, better stability and larger storage capacity than with a single disk. Data reconstruction time for a disk array, for example, a Redundant Array of Independent Disks (RAID), may become longer and longer with growing disk capacity. Typically, longer reconstruction time may imply higher data loss risks.
According to statistics, for example, in DataDomain (data backup product from EMC) customer fields, there may be a number of physical disks failure cases each year in average, and 40% of these failures may cause a data loss. Typically, DataDomain RAID may use RAID-6 data protection algorithm to protect data, which may tolerate 2 physical disks failure simultaneously. However, in practice, if data reconstruction time is longer, the probability of a plurality of physical disks failure may be higher during data reconstruction period.